Platelet function tests are widely used as congenital platelet function abnormality or pre-operative screening tests, and are particularly important for differentiating hemorrhagic diseases caused by congenital or acquired platelet function abnormalities among hemorrhagic diseases having no platelet numerical abnormalities.
Recently, such platelet function tests have come to be widely used to test for increased hemorrhagic tendency as an effect of an anti-platelet drug, which is used for the treatment and prevention of cardiovascular diseases, or to test for resistance to a drug.
A bleeding time (BT) test is a bleeding-time measurement test that was developed about 100 years ago and has been used as a platelet function screening test to date. However, there are problems in that the platelet function test currently in use is difficult to standardize, has low clinical usefulness, and requires the use of an invasive method. Accordingly, an objective measurement method for measuring the platelet function is required.
In the case of a platelet function analyzer (e.g.: PFA-100), which is designed to solve the above-described problems and which is used as a technique for measuring the platelet function, in order to measure the characteristic of aggregation of platelets caused by a von Willebrand factor (vWF) activated at a high shear rate, the clogging time that is required for clogging of orifice holes of an orifice, which is coated with collagen, adenosine diphosphate (ADP), or epinephrine, due to aggregation of platelets after enabling whole blood to flow through a long capillary at a high shear rate is measured using a pressure or a flow rate.
In order to perform the platelet function test, it is inevitable to depend on the function of the vWF, the test is dependent on the hematocrit (Hct), and the anti-aspirin or anti-clopidogrel test cannot be performed, which are considered to be drawbacks. Further, there is a drawback in that testing costs are increased due to the necessity of a two-stage test process for the platelet function test.
In particular, blood samples must be exposed at a high shear rate for a predetermined period of time or longer in order to activate the vWF. For this purpose, PFA-100 adopts a method of enabling blood to rapidly flow through a very long capillary. However, this method has problems in that a large amount of blood is required and that the vWF located at the center of the tube, at which the shear rate is a minimum, is not activated even though the vWF located near the capillary wall, at which the shear rate is a maximum, is easily activated. This may cause a problem in the repeatability of the test result.
In order to solve the above-described problems, Korean Patent Registration No. 10-1193566 proposes a micro-chip-based platelet multifunction testing device. The device includes a sample storage chamber in which a blood sample is received, an stirrer provided in the sample storage chamber to induce a shear flow in the blood sample, parallel channels provided to form a plurality of paths through which the blood stirred using the stirrer flows, a vacuum device connected to the ends of the parallel channels to enable the stirred blood to flow through the parallel channels while maintaining a constant pressure, a light source provided at the rear end of the parallel channels to radiate light to the parallel channels, and an image sensor which receives the light transmitted through the blood in the parallel channels and which converts the light into an electrical signal, thus measuring the flow rate of blood. Accordingly, it is possible to test a plurality of platelet functions by a single test, and an effect of not only reducing the test time but also reducing the testing costs is provided.
However, in the case of the micro-chip-based platelet multifunction testing device, basically, the blood sample is stirred in one sample storage chamber and made to flow through a plurality of parallel channels, and the absolute flow distance of the blood is measured, thereby testing the function of the platelets. Accordingly, the problem of variation in the flow distance of the blood depending on the viscosity or the size of the hematocrit of the blood of a subject, regardless of activation of the platelets, has not yet been solved. Further, the problem of absolute dependency on the function of the vWF has not yet been solved, and there is a drawback in that a drug reaction test for anti-platelet agents cannot be performed.
For example, when the blood of a subject has a high viscosity, the flow distance of the blood flowing through the parallel channels may be shortened, and this phenomenon may lead to errors in judging the platelets to be activated.
Therefore, there is a demand for developing a novel testing chip, testing device, and testing method which can remove, from the test, the undesired influence of the viscosity, the hematocrit, or the vWF of the blood on a technology in which the transfer distance of the blood is judged using the extent of activation of platelets due to the shearing force or the extent of reaction of the platelets according to the anti-platelet agent.